Stencil sheet and method of manufacturing the same



Patented June 17, 1930 UNITED STATES" PATENT OFFICE ALEX BROOKING- DAVIS, OF CINCINNATI, OHIO, ASSIGNOR TO A. B. DICK COMPANY, OF

CHICAGO, ILLINOIS, A CORPORATION'OF ILLINOIS STENCIL SHEET AND METHOD OF MANUFACTURING THE SAME No Drawing.

This application is a continuation of an application filed by me October 7, 1924, for Cellulose ester compositions, Serial No. 742,266.

This invention relates to stencil sheets and to a method of manufacturing the same.

The principal object of this invention is to provide a stencil sheet which is'readily and easily stencilizable by means of either.

type or stylus, to present stencil openings which are well opened, clean-cut, andclear, so that the printed impressions produced by the stencil will be well and evenly inked, clean-cut and clear.

A further object of this invention is to provide a stencil sheet of the character described which is not expensive or difficult to manufacture, and one which requires for its manufacture only commercially available materials. A

A further. object of this invention is to a provide a sheet of the character described inafter.

which is durable andlasting, being capable of surviving crumpling,rcreasing and handling without evil effect, and will retain unimpalred over a long period of time its ability to be stencilized or to yield satisfactory printing.

Another object of this invention is to provide a method of manufacturing a stencil sheet of the character 'referred to, which method tends to yield sheets of the desired quality uniformly, and to provide a method which is suitable for the manufacture and sale on a commercial scale of stencil sheets having the, superior characteristics referred to above.- i

Other objects of this invention will be in part obvious and in part pointed out herestances. I incorporatesuch a substance in a suitable cellulose colloid dissolved in a suitable solvent to form the stencil sheet coating compound, and then produce the Application filed October 26, 1926. Serial No. 144,403.

stencil sheet by coating sheets of suitable base material, such as yoshino, or other suitable porous, open-weave material, with this compound, and allowing the coated In further illustration of my invention the following examples, of methods of making stencil coating compounds are presented: v

1. To a mixture of 100 parts of 5% solution of nitrocellulose dissolved in ether25% alcohol, there may be added 5 parts of propionyl diacetin.

2. To a mixture of 100 parts of 5% solution of nitrocellulose dissolved 'in '7 5% ether25% alcohol, there may be added 5. 7

parts of butyryl diacetin.

Sheets of suitable base material may be coated with either compound. 'Upon the evaporation of the volatile solvent from either coating it Will be found that the gly- 'cerol ester has incorporated itself with the nitrocellulose with-the effect of endowing the mass with softness and flexibility, and

that the sheet will be possessed of the other desirable characteristics mentioned heretofore. I i

The mono diand'tri-acetins formed by esterifying glycerol with acetic acid are already known to be suitable agents for incorporatingin plastic pyroxylin masses,'but all these substances possess disadvantages for stencil manufacture, in that the monoacetin and diacetin are quite hygroscopic, and even the triacetin possesses some hygroscopicity.

When, however, at least one hydroxyl of the glycerol molecule is esterified with a fattyv acidof higher molecular weight than acetic,

' the boiling points are raised, and this in itself constitutes a distinct advantage for stencil sheet manufacture, as the substances are less volatile. As above mentioned, glycerol is a suitable polyhydric alcohol, and when two hydroxyls of the glycerol molecule have been esterified with acetic acid and the third hydroxyl then esterified with an acid of higher molecular weight than acetic acid, compounds are obtained which possess distinct advantages over those substances obtained Where all three hydroxyls havebeen esterified in a uniform manner, as by the use of a single acid, such as acetic acid or formic acid.

Diaceto glycerol propionate may readily be produced by esterifying glycerol with mixtures of acetic and propionic anhydride, or it may be prepared more cheaply by esterifying glycerol by means of acetic anhydride to which has been added a portion of anhydrousor nearly anhydrous propionic .acid, both of which substances are obtainable in quantity commercially at the present time. Glycerol esterified in this manner, yielding diaceto glycerol propionat'e, shows a boiling point for the technically pure sub stance of 263 to .270 degrees G.-approximately 10 degrees above the boiling point of pure triacetin. Again, glycerol may be esterified with acetic anhydride to which has been added one molecular portion of J to those skilled in the art that still higher butyric acid, in which case there is obtained technically pure diaceto glycerol butyrate, and again it is foundthat the higher molecular weight of the butyric acid raises the boiling point, the technically pure substance boiling at approximately 274 to 27 8 degrees C. Both of these substances mentioned are less soluble in water and less hygroscopic than triacetin and they maintain this advantage When incorporated in plastic pyroxylm masses or in masses suitable for the formation of films, and, therefore, when used for stencil sheet coatings produce a superior product for the purpose desired. In vlew of this disclosureit will be evident acids than butyric may be employed to advantagein producing these mixed esters for stenc1l sheet manufacture. These substances are particularly desirable for incorporation 1n pyroxylm stencil sheet coatings, since in these a high degree of softness and flexibllity is desired. They incorporate perfectly with pyroxylin or other forms of cellulose.

For the specific mixed esters mentioned above, other polyhydric alcohols than glycerme may be used, such for instance as the glycols, and whenall the hydroxyl hydrogens have been replaced and the substance rendered anhydrous, they possess the valuable properties of being less hygroscopic,

formic acid. less soluble 1n water, and having a higher' boiling point than the acetyl derivatives pf the parent substance, and, in certain -1n stances, other properties whichwork to their advantage in themanufacture of cellulose If desired, the softness and flexibility may be still further emphasized when other'mods ifying agents\ as Well are mixed with'the pyroxylin solutions as plasticizers. Among such agents, I may mention chlorinated naphthalene and other halogenated aromatic and aliphatic compounds.

\Vhat I claim is:

1. A stencil sheet of the character described, comprising base material having a type impressible cellulose compound coating including polyhydric alcohol ununiformly esterified by means of acetic acid and propionie acid.

2. A stencil sheet of the character described, comprising base material having a type impressible cellulose compound coatingv including glycerol ununiformly esterified by means of anhydrous acetic acid and propionic acid.

3. A- stencil sheet of the character described, comprising base material having a coating including cellulose nitrate and diaceto glycerol propionate. I

4. A stencil sheet of the character described, comprising base material having a coating including cellulose nitrate and dipropionyl diacet in in the relative ratio of twenty parts of solution to onepart propionyl diacetin.

7. A stencil sheet of the character described, comprising base material having a type impressible cellulose compound stencil coating including polyhydric alcohol nonuniformly esterified by organic acids having different molecular weights, one of said acids having a higher molecular weight than 8. A stencil sheet of} the character described comprising base material having a type impressible cellulose compound stencil coating includin polyhydric alcohol nonuniformly esteriiled by different fatty acids one of such acids being acetic acid and another being an acid having higher molecular Weight than acetic acid.

9. A stencil sheet of the character described, comprising base material having type-impressible cellulose compound stencir coating-including aircster of apolyhydric alcohol at least two hydroxyl groups of which have been replaced by radieles of dif ferent acids, one of which contains at least two carbon atoms.

10. A stencil sheet of the character described comprising base material having a type-irnpressible cellulose compound stencil coating including an ester of a polyhydric alcohol at least two hydroxyl groups of which have been replaced by radieles of different acids, one of which contains at least three carbon atoms.-

This specification signed this 15th day of October, 1926. I

- ALEX BROOKING DAVIS. 

